"as if [heretics] could be kept in the city of God indifferently without any correction"

     "But the devil, seeing the temples of the demons deserted, and the human race running to the name of the liberating Mediator, has moved the heretics under the Christian name to resist the Christian doctrine, as if they could be kept indifferently in the city of God without any correction, just as the city of confusion indifferently held the philosophers who were of diverse and adverse opinions.  Those, therefore, in the Church of Christ who savour anything morbid and depraved, and, on being corrected that they may savour what is wholesome and right, contumaciously resist, and will not amend their pestiferous and deadly dogmas, but persist in defending them, become heretics, and, going without, are to be reckoned as enemies who serve for her discipline.  For even thus they profit by their wickedness those true catholic members of Christ, since God makes a good use even of the wicked, and all things work together for good to them that love Him.  For all the enemies of the Church, whatever error blinds or malice depraves them, exercise her patience if they receive the power to afflict her corporally; and if they only oppose her by wicked thought, they exercise her wisdom:  but at the same time, if these enemies are loved, they exercise her benevolence, or even her benificence, whether she deals with them by persuasive doctrine or by terrible discipline."

     St. Augustine, City of God 18.51, trans. Dods.  =CSEL 40.2, 351-352.